A New and Efficient Preparation of Cyclic Carbodiimides from Bis(iminophosphoranes) and the System Boc2O/DMAP

Article abstract of DOI:10.1021/jo00103a022

A one-pot synthesis of cyclic carbodiimides which involves reaction of C,C-bis(aryliminophosphoranes) connected by aliphatic bridges with Boc2O in the presence of DMAP is described.The method is also applicable when a heteroatom such as oxygen or nitrogen is incorporated into the tether connecting the two aromatic rings.A conformation study has been carried out on carbodiimide 23a, which possess a central nine-membered ring, using 1H NMR spectroscopy and semiempirical as well as molecular mechanics calculations.